TKA Balancing
The technical term for hyperextension is this
What is recurvatum?
The femur knee center in Mako Patient Landmarks is located in the same area as where this manual knee instrument is inserted
What is the intermedullary alignment rod?
The medical epicondyle patient landmark is taken here
What is the sulcus?
When entering bone prep, the checkpoint won't pass. What's your first step?
What is go to registration and have the surgeon walk the bone with the blue probe verifying three planes.
How many tibial inserts do we have in the Triathlon portfolio and what are they called?
4; CS, CR, PS, TS
The reasoning behind balancing to 18's is this
What is the nearest round number of the thickness of our components with a 9mm insert (17.5 mm)?
Rotation of the femur on a manual knee is referenced off of this
PCA (Posterior Condylar Axis)
Your lateral and medial malleoli points should be located here
The most prominent/palpable regions of the malleoli
Your scrub-tech registers the robot prior to the case. As he's setting up his back table he realizes all his discs weren't down on his registration endefector. What do you suggest and why?
Re-register with discs all the way down to maintain the accuracy of the system as our cuts could be off the distance that the disc was sitting proud.
Our cemented CR and PS femurs have different dimensions as our cementless CR and PS femurs to create an adequate cement mantel. True or false?
What is 30
To check for notching prior to cutting in Mako, we reference our 3D bone model. In manual cases, notching is assessed using this
An angel wing inserted through the femoral sizer into a size specific slot
If a patient has a valgus knee, these are the pre-planning parameters for the tibia
5mm off the medial side
You've re-registered the femur once and the overall accuracy is still off. What would your next step be?
Have the surgeon redo patient landmarks, DO NOT erase your fine registration.
What is the additional step you must do when using a universal baseplate?
You must use the boss reamer to drill for the stem (length specific)
40 = ? when computing balancing numbers
What is 1mm?
In Mako we can make .5 mm adjustments to our resection depths. In manual knees, what are the set resection depth off the distal femur of the non diseased side?
8mm or 10mm
If a patient has >30 external to the PCA what does this mean for intra-op parameters?
You can add internal rotation until you get down to 30 external to the PCA if needed
You can't checkpoint into the saw, the drape was not bunched, the MICs assembly is tightened and you've tightened the base array and re-registered, but it still won't check point. What do you do?
You have the wrong saw blade
The Triathlon femur grows in which direction?
In the AP direction and only increases anteriorly
What should you reconsider when a patient has a hip replacement when balancing a TKA?
Flexion contracture as the computed mechanical alignment could be showing a flexion contracture or hyper extension due to falsely calculated anterior bow from a ante or retroverted cup and therefore the surgeon should go off clinical assessment
Flexion is set in a manual femur using these two tools.
Rigid intermedullary (IM) rod or flexible IM rod
If a size 5 femur fits perfectly A to P (50 flexion with no notching) but is overhanging medial to lateral, what is the best way to plan for this case?
See how to get a 4 to fit as oversizing M-L can result in poor patient outcome as the MCL and LCL will become worn due to implant overhang
You've completed your distal femur and tibia cut prior to balancing. After balancing you go try to checkpoint into your tibia to recut and your checkpoint is off. What do you do?
You go to bone registration and have the surgeon walk ONLY uncut bone (remember- bone that has had osteophytes removed is considered CUT bone). If this is a CR/CS, have them verify on the island for transverse plane and walk down tib tub and med/lat. IF bumped array, tighten array and troubleshoot.
Your surgeon decides he wants to go PS prior to balancing, you make all your cuts, trial, and he's happy. He preps his PS box and trials again only to realize he's now tight in flexion and wants to downsize his femur to open up flexion. Can he?
Yes, the PS box size is universal. You would have to downside and anteriorize at least 2mm or anterior reference and downsize and then redo all standard Mako cuts.